The team said he would be re-evaluated Monday.
San Antonio actually went ahead on that play, with Tim Duncan grabbing the loose ball and scoring, wiping out what had been a 12-point Dallas lead only minutes before. Duncan added a free throw, too, and the Spurs were headed to their third straight win since a 1-6 slump.
The Spurs got some breathing room in the tight Western Conference playoff race because the Mavericks are right behind them in the standings. San Antonio also won the season series 3-1, which would help should they wind up tied -- but Dallas may have to worry about just making the playoffs, especially if Nowitzki's injury is as severe as it looked.
The Mavericks lost their third straight, dropping them to 0-8 against teams with winning records since adding Jason Kidd. They are 9-8 overall with the All-Star guard.
At 44-26, Dallas was seventh in the West, ahead of Golden State, which was 42-26 before playing the Lakers on Sunday night. Mavs fans may need to be more concerned about the next team in the standings -- Denver, which was 41-28 before playing Toronto on Sunday afternoon.
Ginobili scored 26 points. He started the big rally with a layup and a 3-pointer, then hit a 3 to cap it. He also was 11-of-11 from the foul line. Dallas took only 11 free throws all game.
Duncan finished with 19 points and 13 rebounds, despite missing 11 of his first 12 shots. He made six of his last nine. Tony Parker scored 13 on 4-of-21 shooting. The Spurs made only 33 percent of their shots.
Jerry Stackhouse led Dallas with 19 points and was automatically ejected with 13.9 seconds after getting his second technical of the game; the other came for using Ginobili's face to help get up after the two collided got tangled up going for a rebound late in the third quarter.
Jason Terry scored 17 points, Josh Howard 13 and Nowitzki had 11. He also had three blocks and was part of the reason Duncan got off to such a rough start.
Kidd had seven points, seven rebounds, five assists and three turnovers.
Notes: Dallas was 29-4 at home before the last three games, losses to the Lakers, Celtics and now San Antonio. ... Spurs F Robert Horry hurt his knee Friday night and didn't play. An MRI showed no problems, but he didn't feel right in pregame warmups. ... Kidd lost his 11th straight game against San Antonio. ... Trying to emphasize his harmony with coach Avery Johnson, Mavs owner Mark Cuban wore a T-shirt that read, "Avery's Team." The two had a heated discussion in Johnson's office after a loss to the Lakers earlier in the week.